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Q & A: Planck scale energy

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Most recent answer: 10/22/2007
Q:
What is Plank Energy and why can’t we use it? I’ve heard there’s quite a lot of power down there at the subatomic level.
- Kevin (age 19)
Arizona
A:
All physical units can be expressed as some combination of the speed of light, c, Planck's constant h_bar (the angular momentum unit), and Newton's universal gravitational constant G. Combining these to give a time gives something around 10^-43 seconds, which corresponds to an energy of some 10^16 ergs.

The point, however, is that this is not the calculation of some energy that's sitting around waiting to be used. It's just the calculation of a natural unit in which to measure energy. If it has a physical significance, it may represent the amount of energy that has to be concentrated in a small scale (the Planck distance, about 10^-32 cm) in order to make weird quantum gravitational things happen.

To get usable energy out of some process, there must be some way for things to fall to a lower energy state than they are now in. That's possible for many nuclei- hence we can get nuclear power- but such nuclear reactions are known and have little to do with the Planck scale.

The Planck distance-time scale is the scale on which our current theory of space and time is likely to break down. If there really is some process on that scale that could settle into a lower energy state, that would mean that the current vacuum is unstable. It could somehow start to collapse to the more stable state, which would destroy any sort of physical structure in the current universe. Something like that probably happened at least once in the early universe, ending the strongly inflationary period of the Big Bang.

These are not processes which I would attempt to 'use'.

Mike W.

(published on 10/22/2007)

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